1. Field of the Invention
The present invention relates to an image forming apparatus a function of scanning a document having a larger size than a flat glass and a scanning method thereof; and, more particularly, to an image forming apparatus which scans a part of an A3-sized document loaded on a flat glass using a scanning sensor having a slightly larger size than an A4 size and moves the A3-sized document so as to scan the rest part thereof and then composes the scanned images, thereby producing an image of the A3-sized document, and a scanning method thereof.
2. Description of Related Art
Generally, an image forming apparatus is a device for printing an input image signal on a printing medium, and classified into a printer, a duplicator, a multi-function printer in which the functions thereof are combined in a single body and the like.
The image forming apparatus includes a scanning part for scanning an image recorded on a document. In order for the scanning part to read information from the document, it is necessary to move a scanning sensor of the scanning part or the document.
Therefore, there are two types for scanning the document, one is a flat bed type in which the scanning sensor is moved in a state that the document is fixed, and the other is a sheet feed type in which the document is moved in a state that the scanning sensor is fixed. Recently, the multi-function printer employs the above-mentioned two types, and FIG. 1 shows an example of such image forming apparatus.
As shown in FIG. 1, the image forming apparatus 50 includes a cover 10 and a main body 30. An automatic document feeder 20 is disposed at the cover 10, and a scanning sensor 40 is disposed at the main body 30 to scan a document fed from the automatic document feeder 20.
The scanning sensor 40 may include a CCM module (CCDM) having a charge coupled device as one of image pickup devices which forms an image of a subject using an electric charge, and a CMOS image sensor (CIS) which scans the document.
The automatic document feeder 20 has a C-shaped passage P for feeding the documents. The documents loaded on a document platform 21 are guided to an upper side of the scanning sensor 40 through a pickup roller 22, a transferring roller 23 and a feeding roller 24. Then, the documents are scanned by the scanning sensor 40 and discharged through a discharging roller 25. As described above, it is possible to facilely scan a large amount of documents using the automatic document feeder 20.
Further, the document may be scanned without the automatic document feeder 20. To this end, after opening the cover 10, the document is aligned on a flat glass 31 disposed at an upper surface of the main body 30, and the scanning operation is performed. Then, the scanning sensor 40 is reciprocated at a lower side of the scanning window in an arrow direction A. Therefore, while the scanning sensor 40 is moved, a single sheet of the document can be scanned without the automatic document feeder 20.
Meanwhile, in the conventional multi-function printer, since the scanning sensor 40 is set on the basis of an A4 size which is most widely used, an image forming apparatus for the A3 size is needed to scan an A3-sized document which is larger than the A4 size.
However, since the image forming apparatus for the A3 size has a scanning sensor twice larger than that of an image forming apparatus for the A4 size, a size of the flat glass and a volume of the image forming apparatus are also increased, thereby increasing a cost of the product. Thus, it is difficult to separately purchase the image forming apparatus for the A3 size, which has a low frequency of use.